Linear phase detector



Aug. 7, 1956 Filed May 4, 1955 J. l. DASPIT LINEAR PHASE DETECTOR 2 Sheets-Sheet l /aA/A'/ @psp/7' JNVENTOR.

BY MKM ug- 7, 1956 .1. l. DASPIT 2,758,277

LINEAR PHASE DETECTOR Filed May 4, 1953 2 Sheets-Sheet 2 ./oA/A/ n @45p/7' Q7/C7, Z. INVENToR.

United States Patent PHASE DETECTOR FJohn'f LDaspit; Los Angeles, Calif., assigner tof'Giltillan fBros.,f:Inc.,=Losi-Angeles,(lalif., a Icorporation of 'Califfoxnia Application May 4,1953, Serial No...3\52,941

`8 Claims. ((1624-85) The ,presentinventionrelatesto means and techniques `.for determiningor computingthe phasel displacement ,of. l.two..cyclically varying. quantities, such as= .sine ...waves, aand-producing or deriving an electricalzquantityvwhich .seri/.esas Ya measure of vthetphase displacement,. such electrical quantityfin thisinstancebeing a continuous volt- ...age whichanayl be positive or negative. depending :upon :whether-the .phase displacement -is leadingy r llagging .-.andzwith :the:intensity otsuch voltage serving1 as an indi- .r cation ot\the.degree or magnitude', of .the .phase displacement lBriefly:` stated, fthe present .invention -involves ,circuitry Yttxwhioh asine .reference voltage is appliediaswell `as-a ssine-wavex-whose.phase wvitht respect tto-said .reference .-voltage is-tobecompared. Each of the two-,sine -waves i...are. ,.sh apedfto .producensquare waves, -the zfundarnental -.frequencyeof.suchnsquare Waves being a'fractional ,-part of :the fundamental frequencyI of `they sine .waves )In 2ihis...cas,e,..asf specifically-shown, the'zfundarnental Ifre- A.gquency.otthessquare -waves `is oneghalf. Ofathetffuudamental frequencyof the sine-waves. The Isquareiwaves `-`derivedV fromthe sinefwaves are4 combined andgdiierent falgebraic .sums..are applied to different channels, one f-.channelrcorresponding toa leading--phaseand a-second channel corresponding-to a. lagging phase. 5 Eachf offthese f .two channels is simultaneously :controlled A int accordance -withta voltagetwhich has. a negative or positive polarity, r.depending-. upon lwhether there is leading-or dag-ging .phase lTheoutput ofeachof such .channels .is applied .to .a` corresponding integrating network, I each .tof-ssiieh :.-integrating networks :controlling a .cathode follower. 'l`he voltage" developed -on eaoh: cathode Yfollower :isaapplied ,thropgh. a. .corresponding yrectitierto a corresponding-con- .-.densers such condensers being interconnected; and.-v applied ...1o. a. common `output terminal for .developing continuous voltage on such terminal, .thepolarity;Ot-.suchfvoltage dsr.=,r.vingas..an.indication lof either.- a .laggingorsleading V,.plrase, as the. case-maybe, andthe magnimdetsuch voltagelrservingas. anfindicationof -the magnitude tot the i,-phase.displacement 1 ltsis, therefore,- ay: generalv lobject .of thissinventionato :q provide-.mproved means r and :techniques whereby 1:the

above. .indicated` results may .be obtained.

Another object of the present invention is..to.-pro vide a'zphase.,-detector of this character in which f there 1 is ipro- =.duced alinear relationshipbetween, on:;the';one;hand, ..phaseidisplacement `between `rtwo ysine .evt/aves, IancLfson the other Lhand, some: convenient .ana-log, '.oraexample,

'ac-continuous voltagedifference.

Anotheri object of the present .invention-ism,V provide ,an-sanangemcnt, t as indicated vin theV previous; paragraph,

wherein the phase. angleranalog zis. a Acontinuous voltage, .f thefpolarity, ofwhich representstthe algebraic; sign-,OR the gphase. angle, i..e., rleading-or flagging.

,.Another.object of fthe present invention is..to;provide .-.iixnproved L means and techniques for representing; i the :3 phasedisplacement .between two sine waves, o1'*..,any ssimialar. cyclically-Narying quantity, l. with :the phase displace- 2,758,277 I'Patented Aug. 7,-.1956

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Jv2 .ment. in therange of..0to 360 degreessbeingsploduced .in terms of.. .a .continuous voltage which. varies linearly and. with..the.cha.nge .in polarity.

, Another .specic :object .of..thel..pr esent ,invention is: .to

provide .improved :meansandntechniques, .in-view.. .otgthe teachings herein, ;tov producen lcontinuous voltagefwhich changes linearly without Achanging polarity-in .accordance -.with .phase, displacementsrangingtrom to 360.`degrees, .or 7201 degrees, or;.rnul t ip1es thereof, depending upon whether.. .the aforementionedsquare twaves are .halvedsin frequently, .quartered 4in frequency, .eighthed ...in frequency, etc.

The features ofythepresent ;invention which `are .be- .lieved .to benovel are. set forth .with .particularityin Afthe appended claims. .This .invention `itself,..both.asto.:its organization, and 'mannerof operation, together ,with -furthei-.zobjeets andadvantages thereof, maybebest .un-

derstoodzby reference to .the p following description .taken inconnection with .the accompanying-drawings ,inI which:

Eigure 1, represents. in schematic Aform. apparatus. Aem- A,.bodying features. of ,the :present invention.

EigureZ- represents a series of wave -formsexisting unden very. diierent .conditions in :the circuitry illustrated :in-Figure 1.

NRefern'ngto Eigure. 1,.,the inputto the circuitry vs hown .thereincomprises apair of` sine Wavesor simil-arly cycli- -..cal1y.: varying.x quantities. :Aso-called sine reference-volt- .age .of..zero phase-is applied from ,thel source-'10 over lead-.liftoa-squarer network. '12. Likewise, a sine volt- ..agerwhosetphase,.-with.respect tothe aforementioned ref- --.,erence.volta-ge, -is..to. beV determined ,is.applied over lead `.11.,to..,a-:like squarer .network 13. The voltage vapplied r-.tothe network-.12 -is fr epresentedtby the sine --wave'16 in Figure` 2; `likewise, the sine ;wave appliedfto the network 1S-is -representedby Athe-sine Iwaveflt' in- Figure 2. The

squarer networks 12 and 13 serve to shape the sine waves .-16 i and 17, respeotively, .into corresponding .square .Waves 1S-.and:"19.-.whichhave 'the same` periodicityfas the .'fsine waves from.whichstheyy are-.deri-Ved, suchtl square vibrator&-20.and..21. `The multivibrators20and21 pro- ',duce-.square ,Waves `represented ,-by the -so-calledt plus-,a

mlminusib. It fis-,understood that the circuitry...described :fabovafon the; one. hand; handling. the fwave- .form-:16. .and

waves 18 .and 519;being; applied .to .corresponding multilwave 24.andv the `so-Grll-led-.-plus bwave-.ZS in Figure 2. It isenotedthatlhe multivibratorst) and 21 serve 'to fhalvefcyclical.frequency vari-ation. 1In .other words,- the .One-fourth, ;.One-.fth,. etc., .l .depending upon vthe range of vibrators: 21;;and 22, ,isy to, provide operation of. a larger .range .ofphasefditference fbetweenfvoltageml and 17,

.without ambiguity-otherwise resulting from change :in vthe polarity of thev voltage vdeveloped across the output resistancey68, it being@ noted thatzthe waves; 16 and 17 undergochangegin polarity every `l80"and by -thus di- VvidillgfIllegfrequencyby.a vfactor lof twothe'voltage across resistanceesqchanges its polarityover acorresponding i.Each-of the .twol multivibrator stages AZtl andA 21 has .two outputs, the;stage.20 havingthe outputsrplusga and minus: a andf-thefstage; .21.;,having the. outputs plusfb. and

3 on the other hand, the wave form 17 are similar and, since as shown in Figure 2, such wave forms 16 and 17 have substantially the same amplitude means is disclosed whereby the amplitudes of wave forms a and b are equal, or substantially equal. The minus a voltage is applied to the so-called leading channel through resistance 26; and likewise, the plus b wave is applied through resistance 27 to the same channel 25' with the result that channel 2S has applied thereto a voltage represented by b minus a. Likewise, the so-called lagging channel 30 has applied thereto a plus a voltage through resistance 32, and also has applied thereto a minus b voltage through resistance 33 with the result that the channel 30 has applied thereto a voltage represented by a minus b. The a -minus b voltage is represented by the wave form 34 in Figure 2 which has a positive portion 34A and a negative portion 34B. It is obvious that the trailing edge of the positive portion 34A is Variable depending upon the magnitude of the phase of the lagging voltage. When there is zero lag, the trailing edge of 34A corresponds to the leading edge and, as a matter of fact, there is in such special case no positive or negative portions of the wave 34. lt is noted that the wave form 34 is obtained by subtracting the wave form 2S from the wave form 24.

Likewise, instead of there being a lagging condition, as illustrated by the sine waves 16 and 17 in Figure 2, the condition represented by the wave form 35 may exist when the voltage 17 leads the reference voltage 16. This wave form 35 contains positive portions 35A and negative portions 35B, the leading edge of the portion 35A being variably positioned in time in accordance with the magnitude of the leading phase condition; and, as a matter of fact, the leading edge corresponds with the trailing edge when the phase difference between the two voltages 16 and 17 is zero, in which case actually there is no positive or negative portions 35A or 35B. Thus, wave form 34 is considered to be applied to the lagging channel 30 and the wave form 35 (when a leading condition exists) is considered to be applied to the leading channel 25.

Each of the channels 25 and 30 is returned to ground through corresponding diodes 31 and 32, each having their positive terminals grounded so that the corresponding negative portions 35B and 34B of the waves 35 and 34 are effectively removed and have no iniluence on the n circuitry later described; and this condition is represented by the shading of the negative pulses 34B and 35B in Figure 2. The shading indicates that these pulses are removed. Also, the outputs derived from the channels 25 and 30 are controlled by corresponding grid conl trolled triodes 37 and 38, each of which has its cathode grounded and its anode connected to corresponding channels or leads 25 and 30. The control grids of the tubes 37 and 38 are controlled simultaneously by the so-called push-pull output of the so-called paraphase or push-pull ampliiier titl. The amplier 40, in turn, is controlled by a voltage of substantially constant intensity but of variable phase depending upon the relative phase of the plus a and plus b waves. For this purpose, the plus a and plus b waves are applied to a phase detector 42 which serves to produce an output voltage having either a positive or negative polarity depending upon whether the plus a Wave leads or lags the plus b wave. This voltage derived from the detector 42 is applied to the amplitude limiting amplifier 44, the output of which is coupled to the paraphase amplitier 40. It is understood that when the output terminal 48A of the amplifier 40 is caused to be positive by the voltage applied thereto from the amplifier 44, the other output terminal B is negative. In other words, the output of the amplifier 40 controls the two limiters 37 and 38 in such a manner that, when the phase is lagging, the b minus a wave form is suppressed altogether and only the positive portion 34A of the a minus b wave 34 has its effect on the measuring circuit described later. Likewise, when there is a leading phase condition, the output of the amplifier 4t2 controls the twolimiters 37 and 38 in such a manner that the a minus b wave is suppressed altogether and only the positive half 35A of the b minus a wave form is allowed to pass to a diierent corresponding measuring circuitry since the output of the ampliier stage 40 comprises two voltages 180 out of phase, as described above, for application to the grids of tubes 37 and 38, two subtractions are involved, as described above, one subtraction being for obtaining a voltage b-a and the other subtraction being for obtaining a voltage a-b, which are applied respectively, to the anodes of devices 37 and 3S. By these techniques a balanced system capable of good practical adjustment is provided in which the output voltage appearing across the resistance 68 is either positive or negative depending upon whether there is a lagging or a leading phase condition.

The so-called duration measuring circuitry 50 for channel 3@ comprises the condenser 56A, fixed resistance 50B and adjustable resistance 50C. An inverter 52 serves to invert the positive portion 34A of the wave form 34 before the same is applied to the condenser 50A. 'The corresponding duration measuring circuitry 53 for channel 25 includes the condenser 53A, resistance 53B and adjustable resistance 53C. The Wave form applied to the condenser 53A (or condenser 50A when the phase is lagging) is indicated by the Wave 61 in Figure 2. The peak to peak amplitude is standardized and constant and the time constant of the circuitry 53A, 53B and 53C is several times the period of the wave 24, so that the peak positive deviation of grid potential, measured from the no signal bias value, is proportional to the duration of the positive part of the rectangular wave form 61. Thus, the peak positive grid swing of the cathode follower tube 55 is proportional to the amount of phase lead. The bias on the grid of tube 55 is so adjusted that the cathode of the tube 55 is substantially zero with reference to the ground in the absence of a signal voltage applied to the control grid of the tube. The positive voltage developed on the cathode of tube 55 is applied through the diode rectier 59 to the condenser 61', it being noted that one terminal of the condenser 61 is grounded and the other one of its terminals is connected through resistance 63 to the output terminal 66 which is returned to ground through the load output resistance 68.

Assuming a lagging phase condition, a signal is applied to the control grid of the cathode follower tube 70, with a peak negative grid deviation from the bias value proportional to the phase lag. The diode 76 is so poled that a negative voltage is developed on the condenser 78 having one of its terminals grounded and the other one of its terminals connected through resistance 80 to the aforementioned terminal 66. Thus, a negative potential appears across condenser 78 proportional to the phase lag, and similarly positive voltage appears across condenser 61 proportional to the phase lead.

While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modiiications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modications as fall within the true spirit and scope of this invention.

I claim:

1. In an arrangement of the character described, a rst source of a first voltage, a second source of a second voltage which has generally the same shape and the same periodicity as said first voltage, first wave shaping means coupled to said first source and functioning to produce a first substantially square wave of lower periodicity than the periodicity of said iirst voltage, second wave shaping means coupled to said second source and producing a second substantially square wave having a periodicity less than the periodicity of said second voltage, a rst channel representing a phase leading condition, a second channel representing a phase lagging condition, means coupled to said rst and second wave shaping means producing a voltage which is representative of the difference between ingreep?? saidfirst and said second square-waves and.:applyingithe isame to-saidfirst channel, means coupledto saidlfirstand secondl'wave shaping means producing a voltagelwhich Y'isfthedifference between said second vand first squareiwaves `:and applying said diferenceto said secondchann'el,` means lcoupled to saidtfirst and second sourcev and controlling said first andV second channels simultaneously to render '.'the r same' alternatively effective in accordance with the` phase `difierence' betweensaid first and second squarehwaves, l condenser `meansfcoupled to saidilfirst-.channel Afor'=producing a substantiallyrcontinuous voltage representative fof the difference voltageapplied tosaid firstand second channels, condenser means coupled to saidsecond channel and producing a substantially continuous voltage which is the measureof'the differencevoltage applied to said second channel, said-first andsecond condenser means being coupled to a common impedance.

2. Afirst-source-ofea-first squarevvave, a second source *of atsecond square -wave-which has'the sameperiodicity as said first wave, a first channel representing a phase leading condition, a second'channelrepresenting a phase lags ging condition, -means coupledfto usaid'ifirst ,andi second sources producing a first difference voltage'whichis representative of the amplitude difference between said first square wave and said second square wave and applying the same to said first channel, means coupled to said first and second sources and producing a voltage which is the difference between said second and first square waves and applying said difference to said second channel, means coupled to said first and second source and controlling said first and second channels simultaneously to render the same alternatively effective in accordance with the phase difference between said first and second square waves, condenser means coupled to said rst channel for producing a substantially continuous voltage representative of said first difference voltage applied t'o said first and second channels, condenser means coupled to said second channel and producing a substantially continuous voltage which is the measure of said second difference voltage applied to said second channel, said first and second condenser means being coupled to a common impedance.

3. in an arrangement of the character described, a first source of a first voltage, a second source of a second voltage which has generally the same shape and the same periodicity as said first voltage, a first channel representing a leading condition, a second channel representing a lagging condition, means coupled to said first and second source for deriving a voltage which is a first difference in amplitude between said first voltage and said second voltage and applying said difference voltage to said first channel, means coupled to said first and second source and deriving a second difference voltage which is the dierence in amplitude between said second voltage and said first voltage, and applying said second difference voltage to said second channel, phase responsive means coupled to said first and second sources and controlling said first and second channels simultaneously to render the same alternatively effective, and means coupled to said first and second channels for deriving a continuous voltage which is representative of either said first difference voltage or said second difference voltage, as the case maybe, depending upon which of said first and second Ychannels is rendered effective.

4g In an arrangement of the character described, a first source of a first voltage, a second source of a second voltage which has generally the same shape and the same periodicity as said first voltage, a first channel representing a leading condition, a second channel representing a lagging condition, means coupled to said first and second source for deriving a voltage which is a first difference in amplitude between said first voltage and said second voltage and applying said difference voltage to said first channel, means coupled to said first and second source and deriving a second difference voltage which is the difference in amplitude between said second voltage and said first voltage, and applying said second difference voltage 'Lto vsaid l secondachannelgfphasef responsive means ucoupled to lsa'idfzfirsttandfisecond sources f and' controlling V:"said :first-.LandI second-channels simultaneously in f accordrance with lthe phase I .differences between said first and 5 rsecond voltages to nrender.said":first and second channels alternativelyeffective, yandi an :output circuit: Ycoupled-to lrbothisaidfrst and secondchannelsfordeveloping aivoltf. age which .tis representative* of either said .first Idilierence "voltage ori'said secondldiferenceivoltage asuthe casemay 10 be depending upon which of said firstfand' secondchan- .nels is rendered effective.

15.'y Infan arrangementaof'the lcharacter described, alfirst usourcei ofLaofirstfv voltage, fa-.secoridsource of a second .voltagewhichfhas lgenerally the"` same 'shape and the same periodicityn as saidfirstvoltage,La'first channel representing :La rleading condition; a1 second vchannel'representing allagging vcondition#meanscoupled `to :said first -andwsecond source forA deriving. .avoltagei which 1 is-vv a 'first difference vin tamplitudefbetween said rsttvoltagelandfsaid seconda/olt- 2() age: and; applying .said differencev voltage to saidifirst` chaneheh/:means ycoupled 'tolsaidfirst candlsecond source =and sderivingz.. a `second differencef-.voltage wvhieh is 'thef difier- :itence in Lamplitudef'b'etween .sad :second voltage andsafid first voltage, and applying said second difference voltage to said second channel, means connected to each of said first and second channels to remove voltage variations therefrom of predetermined polarity, phase sensitive means coupled to said first and second sources and controlling said first and second channels jointly to render the same alternatively effective in accordance with the phase difference between said first and second voltages and an output circuit coupled to both first and second channels for developing a voltage which is representative of either said first difference Voltage or said second difference voltage as the case may be, depending upon which of said first and second channels is rendered effective.

6. In an arrangement of the character described, a first source of a first voltage, a second source of a second voltage which has generally the same shape and the same periodicity as said first voltage, a first channel representing a leading condition, a second channel representing a lagging condition, means coupled to said first and second source for deriving a voltage which is a first difference between said first voltage and said second voltage and 45 applying said difference voltage to said first channel, means coupled to said first and second source and deriving a second difference voltage which is the difference between said second voltage and said first voltage, and applying said second difference voltage to said second channel, 50 phase respons-ive means coupled to said first and second sources and controlling said first and second channels simultaneously to render the same alternatively effective, means coupled to said first and second channels for deriving a continuous voltage which is representative of either said first difference voltage or said second difference voltage as the case may be, depending upon which of said first and second channels is rendered effective, and means connected to said first channel and to said second channel to remove voltage variations of predetermined polarity therefrom.

7. In an arrangement of the character described, a first source of a first voltage, a second source of a second voltage which has generally the same shape and the saine periodicity as said first voltage, a first channel representing a phase leading condition, a second channel representing a phase lagging condition, means coupled between said first source, said second source and first channel for applying to said first channel, a first difference voltage which is the difference in amplitude between said first voltage and said second voltage, means coupled between said first source, said second source, and said second channel for applying a second difference in amplitude between said second voltage and said first voltage, phase sensitive means coupled to said first source and said sec ond source for developing a pair of voltages, each of 75 which is representative of the phase between said first voltage and said second voltage, and applying each of said pair of voltages to a corresponding one of said rst and second channels for rendering said first and second channels alternatively effective, and an integrating net- Work coupled to a corresponding one of said rst and second channels for deriving a voltage representative of which is representative of either said rst difference voltage or said second difference voltage, as the case may be, depending upon which of said first and second channels is rendered effective.

8. In an arrangement of the character described, a rst source of a first cyclically varying voltage, a second source of a second cyclically varying voltage which has generally the same shape and the same periodicity as said first voltage, a rst channel representing a leading condition, a second channel representing a lagging condition, means coupled to said first and second source for deriving a voltage which is the difference between said iirst voltage and said second voltage and applying said difference voltage to said first channel, the last mentioned means including means for reducing the periodicity of said first difference voltage, means coupled to said first and second source and deriving a second difference voltage which is the difference between said second voltage and said first voltage and applying said second difference voltage to said second channel, the last mentioned means including means for reducing the periodicity of said second difference voltage, phase responsive means coupled to said first and second sources and controlling said first and second channels simultaneously to render the same alternatively eiective, means coupled to said first and second channels for deriving a continuous voltage which is representative of either said first diiference voltage or said second difference voltage as the case may be, depending upon which of said first and second channels is rendered effective.

References Cited in the file of this patent UNITED STATES PATENTS Heising June 23, 1942 Andresen June 7, 1949 Abstract of application Serial No. 605,128, published on August 23, 1949. 

